Hitherto, as this type of device, there has been known, for example, the one disclosed in paragraphs 0034 to 0036 and FIG. 15 and FIG. 16 of Japanese Patent Application Laid-Open No. H5-329186 (hereinafter referred to as Patent Document 1). Patent Document 1 describes a device (a walking assistance device) adapted to attach supporting members to the thigh, crus, and foot of each leg of a user and to drive joints, which connect these supporting members, by actuators so as to impart target driving power to the user through the intermediary of the supporting members.
The device described in the aforesaid Patent Document 1 is capable of generating target driving power in a direction in which the user is moving, thereby reducing the driving power required to be generated by the user himself/herself. However, as is obvious from FIG. 15 in Patent Document 1, the weight of the user has to be supported by the user himself/herself, so that a reduction in a load on the user has been unsatisfactory. In addition, the one in Patent Document 1 does not have a technique for compensating for the influences of inertial forces produced due to motions of the user or motions of the supporting members or the actuators, or the gravity acting on the device. Therefore, especially when the user tries to take an agile motion, the user has to bear by himself/herself a force against an inertial force of the device, leading to a possibility of adding to the load on the user rather than reducing the load.
Further, the one disclosed in Patent Document 1 does not have a technique for properly dividing target driving power between the legs of the walking assistance device, so that there has been a possibility that a force not matching a motion of each leg of the user may act on each leg of the user. In addition, according to the one disclosed in Patent Document 1, the supporting members of the walking assistance device are attached to the thigh, the crus, and the foot of each leg of the user, and forces are applied from the supporting members to the thigh, the crus, and the foot of each leg of each leg. This arrangement has been apt to cause the user to feel uncomfortable.
The present invention has been made with a view of the aforesaid background, and it is an object of the invention to provide a control device for a walking assistance device capable of providing a user with an assisting force (lifting force) which makes it possible to properly reduce a force to be supported on a floor by the user himself/herself with his/her leg or legs, while at the same time compensating for, by the walking assistance device, the influence of an inertial force of the device caused by a motion of the user and the influence of gravity acting on the device. It is another object of the invention to provide a control device for a walking assistance device capable of properly distributing an assisting force thereof among leg links associated with the legs of the user.